Pyrometric device



3 t H. B. HENDERSON Er AL 5 PYROMETRI'C DEVICE Filed April 30, 1935Zinnentors B .gergieffion.

an e %A attorney Patented Jan. 21, 1936 UNITED STATES PYROMETRIO DEVICEHerbert B. Henderson and Edward 0. Henderson, New Brighton, Pa.

Application April 30, 1935, Serial No. 19,123

Claims.

This invention relates-to an improved pyrometric device and seeks amongother objects, to provide a reliable indicator of heat work. Heretofore,pyrometric cones, so called, have been ,5 designed primarily as heatindicators so that by observing the cone during the'course of firing,the temperature of the kiln could be reasonably gauged. Such cones haveproven unsatisfactory, however, for many reasons chief among which isthe fact that due to the thickness or mass of said cones they are notuniformly affected by kiln gases with the result that a refractory skinis sometimes formed on the exterior of the cone while the interiorthereof develops a cellular structure. The cone thus assumes abi-refractory characteristic and such cones do not behave uniformlyunder actual firing conditions, with consequent inaccuracy. It may alsobe mentioned that the usual solid cones have a tendency to bloat and dueto their bi-refractory characteristics tend to melt and bend at widelydifferent kiln temperatures and are accordingly inaccurate. Instead ofthe inaccurate method of gauging the extent of heat work in the kiln byproviding 25 a cone intended to function as a heat indicator, thepresent invention is predicated upon a direct approach to the object ofmeasuring the actual work done by the kiln temperature and seeks in thisway, to provide a dependable guide to the firing of ceramic ware. I

A further object of the invention is toprovide a device which, for givensize and thickness consistent with stability, will have a maximum ofsurface exposed for contact by kiln gases, so as 35 to take advantage ofthe various chemical changes and compounds produced by contact withthese gases whereby reaction, which proceeds'from the surface toward theinterior, can

4 be completed in time proportional to the surface area.

A further salient object of the invention, there-f fore, is to provide adevice wherein its entire inner surface, practically speaking, as wellas its entire outer surface will be exposed to the'free 45 circulationof kiln gases, wherein the walls of the device will be thin so that thereaction of the kiln gases may proceed inward from both'surfaces of saidwalls to penetrate the entire mass so 65 ject, to provide a device of ashape adapted, to ace curate as well as easy manufacture, which canstand handling and such that the device will be capable of standingupright in practical use, and wherein the chemical reactions resultingin softening and fusion may proceed without disrupting 5 the mass of thebody of the device to thus provide a reliable guide for the control ofthe heat treatment of ceramic ware.

Other and incidental objects of the invention will appear during thecourse of the following 10 description and in the drawing forming partof this application;

Figure 1 is a perspective view of my improved device.

Figure 2 is a side elevation of the device. 15

Figure 3 is a transverse section. v

Figure 4 is a longitudinal section taken medial- 1y through oneof thewings of the device.

Figure 5 is a perspective view showing a variation in the shape of thedevice. 20

In carrying the invention into effect, our improved pyrometric devicemay be formed in any one of a number of different shapes meeting therequirements of the invention and in Figures 1 to 5 inclusive of thedrawing, we have shown a device the body of which is V-shaped in crosssection. The body' of the device thus comprises diverging wings l0integrally connected at their meeting longitudinal edges. Asparticularly brought out in Figure 2, each of the wings I0 is tapered inwidth towards its upper end so that in side elevation, the body of thedevice is of frhstr'o-pyrarhidal shape. This longitudinal tapering ofthe body of the device is adopted because of the gravitational action inbending under the influence of kiln temperatures, as to accomplishbending at thermal uniformity, the mass of the tip of the body must be aminimum and the mass of the body must gradually increase towards thebase of the body which base serves, in the practical use of the device,as a fulcrum. The cross sectional V-shape of the body in conjunctionwith the gradual widening of the wings I!) toward the base also impartsstability to the device and resistance to fracture, particularly nearthe base of the body where it might snap off.

The base of the body is, of course, the surface or surfaces thereof uponwhich the body rests when arranged in operative upright position upon rthe usual holding plaque within a kiln and in this connection, it shouldbe noted that it is imperative the base be of such contour as to firmlysupport the device in such upright position. Thus, in the instance ofthe cross-sectional V-shaped device, the long bottom edges ll of thewings l provide the base of the body and, due to the divergence of saidedges these edges will, as will be appreciated, rigidly support the bodyupright. It should be noted, however, that the bottom edges of the sidewings H} are tilted or inclined so that the body of the device thusnormally sets at a slight angle, possibly 8 more or less from thevertical, this being done to enhance the thermally accurate bending ofthe device in practical use.

The device may be formed of any suitable plastic or stifi mud and anyapproved process may be followed in producing the device. It should benoted, however, that a V-shaped body, as shown, is eminently suitablefor manufacture by machinery through the use of suitable dies, as bypressing or extrusion methods, in that the device does not possess anypockets or obstructing walls.

Attention is now particularly directed to the fact that the wings in arethin and that each of these wings is of uniform thickness and densitythroughout the length thereof. These characteristics in a pyrometricbody in conjunction with stability and the provision of wholly exposedinner and outer surfaces of a body adapted to stand upright constitutesperhaps the most salient feature of the present invention and in usingthe term thin herein as applied to the wings or walls of the body, athickness not exceeding a maximum of 5 is contemplated. Uniformity ofthickness and density may readily be obtained by pressing the body in amold adapted to exert a uniform pressure on the body so that the devicemay thus be manufactured with accuracy.

As will, now'be perceived, the body of the device provides a structurewherein, for given size, a maximum area is exposed to direct circulationof and contact with kiln gases whereby reaction can be completed in timeproportional to the surface area of a Wall thickness of uniform thinnessand density. Advantage is thus taken of the various chemical changes andcompounds produced by contact of those kiln gases which in the use ofconventional pyrometric cones are frequently injurious. the deviceprovides a structure wherein the kiln gases will not be entrapped by thedevice. In other words, the kiln gases may freely circulate about thewings ll of the body at both sides of said wings and throughout thelength thereof to directly act upon the entire vertical surfaces of thewings.

At this point, it should be noted that in the i use of conventionalthick pyrometric cones, kiln gases penetrate the exposed surface thereofto a shallow depth only and change the character of the surface materialto produce a refractory shell. Thus, in the kiln, the ordinary thickpyrometric device possessing no uniformity of mass in any dimension,assumes, contrary to the results desired, a makeup of an outerrefractory shell and an inner cellular mass. Such a bi-refractory devicedoes not behave dependably under practical firing conditions nor is it areliable guide in kiln firing. Furthermore, certain gases under somekilnconditions react with the surface material of a conventionalpyrometric device to cause such a change in the material that the devicewill melt or fall at erratic and entirely different temperatures thanwhen said gases are absent.

In this connection, it is also to be noted that all so-called pyrometriccones contain an organic binder to, impart the necessary working qualityto the material in molding and to give the finished devicesuflicientstrength when dryv to withstand As will also be perceived, thebody of.

shipping and handling. This organic material is sometimes entrapped inthe heavy thick part of the cone and as the temperature in the kilnrises and gases are developed, swelling and bloating of the cone occursin the thicker portion thereof. Also, the usual cone bodies conta nmineral carbonates which give off gas on heating as do oxides ofminerals when combining to form other minerals during fusion. Fusionlike oxidation proceeds from the outside of the cone body toward thecenter and as the fusion progresses, the body shrinks and becomesdenser, sealing the interior to produce the well known effect of anouter refractory shell and an inner cellular core.

In contrast, thin walls of uniform density and thickness exposed to thefree circulation of kiln gases, as in the present invention, offer amaximum of uniformly exposed surfaces to in turn assure a maximum changein the material of the body by absorption and reaction of thesurrounding atmosphere. Due to the thinness of said walls, fusion oroxidation can proceed from both sides thereof to penetrate the entirethickness of said walls while the decomposition products have a chanceto escape so that there is no swelling or bloating. Fusion mayaccordingly proceed without disrupting the body of the device and as thekiln gases will completely penetrate the thickness of the walls thereof,the entire thickness of said walls will become uniform in compositionand no cellular core will develop. The device of the present inventionis thus monorefractory and advantage is thus taken of the action of thekiln gases to provide a dependable guide to the firing of ceramic warein instances where conventional pyrometric cones will not function in adependable manner.

Exhaustive tests have demonstrated that a pyrometric body having a thinwall of uniform thickness and density, wherein the body isscientifically constructed to stand upright andattain proper bendingupon fusion, and wherein the kiln gases may have a free circulationabout a maximum surface of the walls of said body at both sides of saidwalls, provides a pyrometric device capable of complete thicknesspenetration by the kiln gases to convert the body into a monorefractorysubstance, the thin walls being uniformly afiected under substantiallyall kiln conditions. When the fusion temperature of the refractorymaterial of the body is attained, the body will bend normally. This willoccur at a higher temperature than the normal bending of conventionalpyrometric devices but this feature is of no importance as it is onlynecessary to designate a higher index for the thin walled device of thepresent invention or the user of the device may select by trial, theproper device for this kiln.

In Figure of the drawing, we have shown a variation in the shape of thedevice wherein the body l2 thereof is semi-circular in cross section. Aswill be observed, when the device is arranged in upright position uponthe usual holding plaque, kiln gases may freely circulate about thewalls of the device at both sides thereof. Except as to shape, thedevice of Figure 5 of the drawing possesses all of the characteristicsdescribed in connection with the device of Figures 1 to 4 inclusive andfurther amplification would accordingly appear unnecessary.

Having thus described the invention, we claim:

1. A pyrometric device including a body having thin wall portions lyingin more than one plane and providing a base adapted to support the bodyin upright position, one of said wall portions having its opposite majorsurfaces exposed to the free circulation of kiln gases thereabout whenthe body is disposed upright.

2. A pyrometric device including a body having angularly disposed wallportions providing a base adapted to support the body in uprightposition, one of said wall portions being thin and having its oppositemajor surfaces exposed to the free circulation of kiln gases thereaboutwhen the body is' disposed upright.

3. A pyrometric device including a body having angularly disposed wallportions providing a base adapted to support the body in uprightposition, one of said wall portions being thin and of uniform thicknessand having its opposite major surfaces exposed to the free circulationof kiln gases thereabout when the body is disposed upright.

4. A pyrometric device including a body having angularly disposed wallportions providing a base adapted to support the body in upright posi- 7tion, one of said wall portions being thin and of uniform thickness anddensity throughout at least one dimension thereof and having itsopposite major surfaces exposed to the free circulation of kiln gasesthereabout when the body is disposed upright.

5. A pyrometric device including a body having angularly disposed wallportions providing a base adapted to support the body in uprightposition, the mass of the body gradually increasing towards the basethereof, one of said wall portions being thin and of uniform thicknessand density throughout at least one dimension thereof and having itsopposite major surfaces exposed to the free circulation of kiln gasesthereabout when the body is disposed upright.

HERBERT B. HENDERSON. EDWARD O. HENDERSON.

